Closure mechanism with gas seal

ABSTRACT

A closure mechanism includes a conical discharge nozzle and a shielding tube fitted over the exterior of the discharge nozzle. A snug conical joint is formed by closely complementary conical surfaces of the discharge nozzle and the shielding tube. At least one ring-shaped seal is provided in such joint to prevent exterior air from entering between the discharge nozzle and the shielding tube into the interior of the shielding tube. The ring-shaped seal comprises an annular recess formed in one of the conical surfaces, thereby defining an annular chamber, and an inert gas filling such chamber.

BACKGROUND OF THE INVENTION

The present invention relates to a closure mechanism of the typeoperable alternately for discharging molten metal from a molten metalcontaining vessel and for blocking such discharge, the closure mechanismbeing of the type including a conical discharge nozzle and a shieldingtube fitted over a portion of the exterior of the discharge nozzle.

In molten metal containing vessels, such as casting ladles andtundishes, a molten metal, for example a steel melt, may be dischargedthrough a closure mechanism, for example a stopper lock or a slidinggate closure unit, into an intermediate vessel or to a continuouscasting mold assembly. Closure mechanisms of this type include a lowerdischarge nozzle, for example attached to a sliding plate of a slidingplate closure unit. To this discharge nozzle is attached a protectivetube or shielding tube for the purpose, inter alia, of preventing theenvironmental atmosphere from oxidizing the discharged molten metal.Conventionally there is provided a conical snug fit or joint between thedischarge nozzle and the shielding tube to ensure a reliable seal and toprevent the entrance of surrounding air. Nevertheless, unavoidably someair enters into the interior of the shielding tube along such conicaljoint. The result is that some of the molten metal passing through theshielding tube becomes oxidized, thereby deteriorating the degree ofpurity of the molten metal, for example steel.

In the past, various proposals have been advanced to attempt to overcomethis problem. Thus, it has been attempted to place gas permeable insertsin the shielding tube beneath the discharge nozzle and to supply ashielding gas, such as an inert gas, to such insert. French Pat. No.1,474,632 discloses a device in which a snug fit between the dischargenozzle and the protective tube is not required, and rather wherein anopen boundary zone therebetween is filled with a protective or shieldinggas. This solution however is complex structurally and requires aconsiderable consumption of the protective gas.

SUMMARY OF THE INVENTION

With the above discussion in mind, it is the object of the presentinvention to provide a closure mechanism structure of the type discussedabove, but which is of a structure which prevents, with a high degree ofaccuracy, exterior air from entering into the interior of the shieldingtube.

This object is achieved in accordance with the present invention by theprovision of a snug conical joint formed by closely complimentaryconical surfaces of the discharge nozzle and the shielding tube. Atleast one ring-shaped seal is provided in this joint. In accordance witha preferred arrangement of the present invention, this ring-shaped sealcomprises an annular recess formed in at least one of the conicalsurfaces of the discharge nozzle and the shielding tube. Such recessdefines an annular chamber which is filled with an inert gas.Preferably, the recess is formed in the shielding tube. The recess maybe formed to be of a uniform depth, or alternatively the recess may bewedge-shaped. An inert gas connection opening may extend through theshielding tube and open into the annular chamber. Such connectionopening may be connected to a supply source of the inert gas.

In accordance with a further embodiment of the present invention, anadditional ring-shaped seal of refractory fibrous material may bepositioned between the discharge nozzle and the shielding tube.Specifically, the shielding tube may have therethrough a dischargepassage defining with the conical surface of the shielding tube a step,and the ring-shaped seal formed of refractory fibrous material may bepositioned between the step and the outer end of the discharge nozzle.The discharge passage through the shielding tube may be an innercylindrical surface of the shielding tube.

In accordance with the present invention, air is prevented from passingthrough the conical joint between the discharge nozzle and the shieldingtube by the provision of the annular, inert gas seal. Particularly,after repeated uses of the shielding tube, such that the conicalsurfaces no longer are closely complementary, the annular seal of inertgas still prevents exterior air from passing between the conicalsurfaces. In accordance with the present invention, relatively littleinert gas is consumed, since the shielding or protective gas flows onlyalong actual leaks between the conical surfaces into the interior of theshielding tube. As long as these areas of leakage between the conicalsurfaces are leakproof, only a slight amount of inert gas will beconsumed.

The annular chamber is of a simple construction, since only a singleannular recess need be formed. Such recess may be formed in the outerconical surface of the discharge tube or in the inner conical surface ofthe shielding tube. However, advantageously the connection opening tothe inert gas supply line always should be provided in the body of theshielding tube.

In the embodiment of the present invention employing a refractoryfibrous ring-shaped seal between the outer end of the discharge nozzleand a step in the shielding tube, there are provided a number ofadvantages. Thus, there is provided an increased resistance to the entrytherethrough to the interior of the shielding tube. Additionally, thisarrangement prevents the buildup of solidified metal, thereby making itpossible to use the shielding repeatedly without the necessity ofburning out solidified metal. Burning out of solidified metal wouldchance damage to the annular recess formed in the conical surface of theshielding tube.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will bedescribed in further detail below, with reference to the accompanyingdrawings, wherein:

FIG. 1 is a cross-sectional view of the lower portion of a dischargenozzle and the upper portion of a shielding tube in accordance with oneembodiment of the present invention;

FIG. 2 is a view similar to FIG. 1, but of a second embodiment of thepresent invention; and

FIG. 3 is a view similar to FIGS. 1 and 2, but of a third embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, there is shown the lower portion of adischarge nozzle 1 employable in a closure mechanism of the typeoperable alternately for discharging molten from a molten metalcontaining vessel and for blocking such discharge. The further structureof the closure mechanism is not shown, and it is intended that thepresent invention be employable with any known and conventional suchclosure mechanism structure. Discharge nozzle 1 has therethrough adischarge opening 3, and discharge nozzle 1 has, at least on the lowerportion thereof, an exterior conical surface 2. A protective orshielding tube 4 has an upper portion 5 having an inner conical surface6 joining a lower discharge passage which conventionally is cylindrical.The conical surfaces 2 and 6 are closely complementary to define a tightor snug conical joint between elements 1 and 4. The lower end ofshielding tube 4 is not illustrated, but is intended to extend into anintermediate vessel or a continuous casting mold, as is known in theart.

At least one ring-shaped seal is provided in the joint between conicalsurfaces 2, 6. Specifically, such ring-shaped seal is defined by anannular chamber 8 formed by an annular recess formed in at least one ofthe conical surfaces 2, 6. In the arrangement illustrated, the recess isformed in the conical surface 6 of shielding tube 4, and such recess isa ring-shaped recess 10 of uniform depth. An inert gas connectionopening 9 passes through upper portion 5 of shielding tube 4. Opening 9is adapted to be connected to an inert gas supply line and opens intoannular chamber 8. Accordingly, annular chamber 8 is filled continuallywith inert gas.

The apparatus of FIG. 1 operates in the following manner. Thus, whenmolten metal passes through outlet opening 3 and enters the interior ofshielding tube 4, a reduced pressure condition is created because of thecross-sectional expansion of the interior of shielding tube 4 withrespect to the lower end 7 of discharge nozzle 1. This has the tendencyto cause external environmental air to be drawn inwardly along theconical joint, i.e. generally downwardly as shown in FIG. 1. However,the ring-shaped seal formed by the inert gas filled annular chamber 8prevents air from being drawn inwardly. This protects the metaldischarge passing through shielding tube 4 from oxidation.

If the joint between the conical surfaces 2, 6 is not entirelyleakproof, which especially can happen after repeated uses of theshielding tube 4, the shielding or protective inert gas supplied fromopening 9 and into chamber 8 will be caused to flow inwardly onlybetween those areas of the conical surfaces actually having leaks. Byincreasing the supply pressure of the inert gas, an effective purging ofinert gas, for example argon, can be achieved through the shielding tube4 into the intermediate vessel to eliminate non-metal inclusions.

FIG. 1 shows relative dimensions of the location of the ring-shapedseal. Thus, H₂ indicates the total length of the joint, i.e. the totallength through which exterior environmental air would have to pass toreach the interior of shielding tube 4. H₁ indicates that a substantialportion of the length H₂ is protected by the inert gas in annularchamber 8.

The embodiment of FIG. 2 is similar to the embodiment of FIG. 1, withthe exception that the chamber 8 is defined by a wedge-shaped recess 11formed in the inner conical surface 6 of the shielding tube 4. Recess 11is somewhat easier to form that recess 10. Otherwise, the embodiment ofFIG. 2 operates in the same manner, as the embodiment of FIG. 1.

It also is possible in accordance with the present invention to providean additional ring-shaped seal of a refractory fibrous materialpositioned between the discharge nozzle and the shielding tube. Such anarrangement is shown in the embodiment of FIG. 3. Thus, shielding tube 4has formed in the interior thereof a step 12 defined between conicalsurface 6 and the discharge passage of the shielding tube. A ring-shapedseal 13 formed from a compressable ceramic refractory fibrous materialis positioned on step 12, and the outer end 7 of discharge nozzle 1rests on seal 13. Those of ordinary skill in the art will understand thetype of materials which may be employed to form seal 13. The embodimentof FIG. 3 operates substantially in the same manner as the embodiment ofFIG. 1. Seal 13 improves sealing between the discharge nozzle and theshielding tube, i.e. between annular chamber 8 and the interior of theshielding tube. If the shielding tube is used repeatedly, a new seal 13can be inserted after each use. FIG. 3 shows the diameter of thedischarge passage through shielding tube 4 being smaller than that ofoutlet opening of discharge nozzle 1. However, such diameters may be thesame, since they are both cylindrical. Thereby, during the discharge ofmolten metal, the reduction in pressure will be less, such that thesealing requirements will be less stringent, as there will be less of atendency for exterior air to be drawn into the interior of the shieldingtube.

In the devices of the present invention, it is possible to achievereliable sealing without the provision of gas permeable inserts in theannular chamber 8.

The present invention has been described and illustrated with regard toparticularly preferred embodiments thereof. However, it is to beunderstood that various changes and modifications may be made to thespecifically described and illustrated structure without departing fromthe scope of the present invention.

We claim:
 1. In a closure mechanism of the type operable alternately fordischarging molten metal from a molten metal containing vessel and forblocking such discharge, said closure mechanism being of the typeincluding a conical discharge nozzle and a shielding tube fitted overthe exterior of said discharge nozzle, the improvement of means forpreventing exterior air from entering between said discharge nozzle andsaid shielding tube into the interior of said shielding tube, saidpreventing means comprising:a conical joint formed by conical surfacesof said discharge nozzle and said shielding tube, said conical surfacesof said discharge nozzle and said shielding tube being closelycomplementary .[.and in abutment.]. .Iadd.without an open spacetherebetween.Iaddend., thereby forming a snug said conical joint; and atleast one ring-shaped seal in said joint, said ring-shaped sealcomprising an annular recess formed in one of said concial surfaces,thereby defining an annular chamber, and an inert gas filling saidchamber.
 2. The improvement claimed in claim 1, wherein said recess isformed in said shielding tube.
 3. The improvement claimed in claim 1,wherein said recess is formed in said one conical surface to a uniformdepth.
 4. The improvement claimed in claim 1, wherein said recess iswedge-shaped.
 5. The improvement claimed in claim 1, further comprisingan inert gas connection opening extending through said shielding tubeand opening into said chamber.
 6. The improvement claimed in claim 1,further comprising a second ring-shaped seal of refractory fibrousmaterial positioned between said discharge nozzle and said shieldingtube.
 7. The improvement claimed in claim 6, wherein said shielding tubehas therethrough a discharge passage defining with said conical surfacetube a step, and said second ring-shaped seal is positioned between saidstep and the outer end of said discharge nozzle.
 8. The improvementclaimed in claim 7, wherein said discharge passage is defined by aninner cylindrical surface of said shielding tube.